1. Field of the Invention
The invention relates in general to a wireless control system and a wireless network expansion method applied thereto, and more particularly to a system and its corresponding method in which Bluetooth wireless transmission is performed and controlled devices configured for the system are capable of switching between two roles so that the number of controlled devices can be extended and increased.
2. Description of the Related Art
Along with the advance in the technology of wireless transmission, related mobile computation devices or wireless transmission controlling devices have become popular in people's everyday life. Due to the features of electromagnetic waves, the transmission and reception of signals between devices are no more subject to the inconvenience and limitation encountered in the connection of physical wires. There are a large variety of products, such as information, communication, and entertainment products, employing wireless transmission. Examples of the products employing wireless transmission comprise notebook computer, keyboard, mouse, fax machines, projectors, printers, scanners, digital cameras, mobile phones, personal digital assistant, tablet PC, network cameras, TVs, stereos, speakers, headphones, microphones and modems. The said products can further be integrated with the Internet to expand functions or form a wireless local area network (WLAN) to control related devices within a particular range.
In terms of current technologies, wireless transmission can adopt wireless protocols or other related ways. For example, microwave, radio frequency (RF), laser, Wi-Fi (conformed to the IEEE 802.11 standard), third generation (3G), long term evolution (LTE) technology, fourth generation (4G), worldwide interoperability for microwave access (WiMAX), infrared (IR), Bluetooth, ZigBee (conformed to the IEEE 802.15.4 standard) or radio frequency identification (RFID) can be used in related wireless devices according to actual needs.
Thus, different transmission specifications or protocols have respective transmission frequency bands, transmission rates, transmission distances or loadable data, and can be used according to the needs of application. For example, Bluetooth is a wireless signal transmission technology conformed to the IEEE 802.15.1 standard and can achieve wireless signal transmission within a short distance (dozens of meters) by using a frequency band of 2.45 GHz. Bluetooth technology, advantageously featured by low power consumption, small chip size and low cost, is for connecting related wireless devices within a particular range and can be used in the control of wireless signal transmission within a short distance. For example, Bluetooth can be used for connecting a notebook computer and a peripheral device (such as a printer, a keyboard or a mouse), connecting a notebook computer and a personal digital assistant, or connecting a mobile phone and an earphone to form a wireless personal area network (WPAN).
However, different transmission specifications or protocols have different features and are subjected to different transmission restrictions or disadvantages. Let the current technology of Bluetooth wireless transmission be taken for example. Although the transmission distance within the WLAN is increased, the number of devices connected within the WLAN is still restricted. To put it in greater details, a Bluetooth network can only have 8 Bluetooth devices at most. Of the 8 Bluetooth devices, one is central control end (or control host), and the other 7 devices are controlled ends (or user ends). That is, one central control end can only connect and control 7 controlled devices in a one-to-one manner. If there are more than 7 controlled devices configured for a Bluetooth network or system, the original system control needs to be adjusted to collaborate with a cabled design. Although the number of controlled devices can be expanded and increased, system control cannot be implemented by way of wireless transmission only.